Devices are known for blow molding a hollow body of thermoplastic synthetic material having a flange ring projecting outward from the circumferential wall of the hollow body. These blow molding devices typically have a recess along a continuous annular region in which an external flange ring of the hollow body is formed after the initial blowing process. The flange ring is produced by compressing the wall portion of the hollow body, where it is located in the annual recess, into a solid ring by driving a movable mold slide in an axial direction toward another mold part.
Flanges on vessels of synthetic material may be made using a prefabricated flange part. Thus it is known, for example, that a prefabricated flange may be placed in a blow molding device as a separate injection molded part. This flange may then be welded on the outer wall of the vessel in the manufacturing process or blow molding of the vessel.
The flange rings formed by blow molding from the wall of the hollow body or with a prefabricated flange part are used in closed hollow bodies, for example, bunged vessels, as roll hoops or transport rings. In parallelpiped hollow bodies, the closed flanged projections alternatively serve as wall reinforcements.
Vessels of synthetic material capable of use with lids of synthetic material; that is, the so-called wide-mouth drums, are generally understood to include large-volume containers or vessels, for example, of 220-L capacity, having a fill opening and a lid which is essentially the same size as the diameter of the vessel. In these constructions, the flange ring of the vessel consists of a compressed surface flange which, for example, pursuant to U.S. Pat. No. 4,177,934 is arranged at some distance under the vessel opening. Against this flange rests a cooperating flange of the turned-up lid of the vessel. The lid, in turn, sits on the neck of the opening of the vessel.
The lid-edge flange conforms in its radial extension with the surface flange of the vessel and transmits stacking forces into the wall of the vessel in the axial direction. In the locked position, the lid is fastened on the vessel by a clamping ring engaging over the lid edge flange on the one hand and engaging under the vessel surface flange on the other.
Lids of hard synthetic material for vessels are customarily pre-fabricated as injection molded parts in a separate operation. In addition to a separate injection molding manufacturing process, special injection molding tools are likewise required for this.